FCFSPersistentQueue.java

package entropy.vjob.queue;
/*
 * Copyright (c) 2010 Ecole des Mines de Nantes.
 *
 *      This file is part of Entropy.
 *
 *      Entropy is free software: you can redistribute it and/or modify
 *      it under the terms of the GNU Lesser General Public License as published by
 *      the Free Software Foundation, either version 3 of the License, or
 *      (at your option) any later version.
 *
 *      Entropy is distributed in the hope that it will be useful,
 *      but WITHOUT ANY WARRANTY; without even the implied warranty of
 *      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *      GNU Lesser General Public License for more details.
 *
 *      You should have received a copy of the GNU Lesser General Public License
 *      along with Entropy.  If not, see <http://www.gnu.org/licenses/>.
 */


import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.LinkedList;
import java.util.List;

import entropy.vjob.VJob;
import entropy.vjob.builder.VJobBuilder;
import entropy.vjob.builder.VJobBuilderException;

/**
 * A simple storable queue. All the vjobs are stored into a folder.
 * VJob can be added (removed) either using the add(remove) method, or
 * bu putting(deleting) the vjob in the folder.
 *
 * @author Fabien Hermenier
 */
public class FCFSPersistentQueue extends VJobsPool {

    /**
     * Compare the file by their modification date. Older first
     */
    private static Comparator<File> olderFirst = new Comparator<File>() {

        @Override
        public int compare(File f1, File f2) {
            return (int) (f1.lastModified() - f2.lastModified());
        }
    };

    /**
     * The current directory that store VJobs.
     */
    private File rootDir = new File("./vjobs");

    /**
     * The extension of the file.
     */
    public static final String EXTENSION = ".btrp";

    /**
     * The builder to create the VJob from a file.
     */
    private VJobBuilder builder;

    /**
     * Make a new queue.
     * If the folder describing the queue does not exists, it is created.
     *
     * @param b      the builder that constructs VJobs
     * @param folder the folder where to store the vjobs.
     */
    public FCFSPersistentQueue(VJobBuilder b, File folder) {
        builder = b;
        rootDir = folder;
        if (!rootDir.exists() && !rootDir.mkdirs()) {
            getLogger().info("Unable to create folder '" + folder + "'");
        }
    }

    /**
     * Get the VJobs by browsing the folder.
     *
     * @return a list of vjobs, may be empty
     */
    @Override
    public List<VJob> getRunningPriorities() {
        List<VJob> readed = new LinkedList<VJob>();
        List<File> files = new ArrayList<File>();
        for (File f : this.rootDir.listFiles()) {
            if (f.getName().endsWith(EXTENSION)) {
                files.add(f);
            } else {
                getLogger().debug("Ignoring '" + f.getName() + "'");
            }
        }
        Collections.sort(files, olderFirst);
        for (File f : files) {
            try {
                VJob l = this.builder.build(removeExtension(f), f);
                readed.add(l);
            } catch (IOException e) {
                getLogger().debug("Skipping vJob in " + f.getName() + ": " + e.getMessage());
            } catch (VJobBuilderException e) {
                getLogger().debug("Skipping vJob in " + f.getName() + ": " + e.getMessage());
            }
        }
        return readed;
    }

    /**
     * Put the VJob in the queue folder.
     *
     * @param v the vjob to add
     * @return true if the vjob is stored into the queue folder.
     */
    @Override
    public boolean add(VJob v) {
        try {
            v.store(new File(buildPath(v.id())));
        } catch (IOException e) {
            getLogger().warn(e.getMessage());
            return false;
        }
        return true;
    }

    /**
     * Remove the VJob from the queue folder.
     *
     * @param v the vjob to remove
     * @return true if the vjob was deleted
     */
    @Override
    public boolean remove(VJob v) {
        File f = new File(buildPath(v.id()));
        return f.exists() && f.delete();
    }

    @Override
    public VJob get(String id) {
        File f = new File(buildPath(id));
        if (!f.exists()) {
            return null;
        }
        try {
            return this.builder.build(removeExtension(f), f);
        } catch (IOException e) {
            getLogger().debug("Ignoring vJob in " + f.getName() + ": " + e.getMessage());
            return null;
        } catch (VJobBuilderException e) {
            getLogger().debug("Ignoring vJob in " + f.getName() + ": " + e.getMessage());
            return null;
        }

    }


    /**
     * Build the absolute path of the vjob.
     *
     * @param id the identifier of the vjob
     * @return the absolute path
     */
    private String buildPath(String id) {
        StringBuilder b = new StringBuilder();
        b.append(getFolder().getAbsolutePath());
        b.append(File.separator);
        b.append(id);
        b.append(EXTENSION);
        return b.toString();

    }

    /**
     * Remove the extension of a file name
     *
     * @param f the file
     * @return the name
     */
    private String removeExtension(File f) {
        String name = f.getName();
        return name.substring(0, name.indexOf(EXTENSION));
    }

    /**
     * Get the directory used to store the vjobs description.
     *
     * @return an existing folder
     */
    public File getFolder() {
        return this.rootDir;
    }
}